I have recently lost 3 fish. One seemed to be unable to release her eggs. The other two died of unknown causes. So I am looking for advice on how to properly sanitize things to make sure nothing gets passed on.
I know bleach is one way, but not sure about it.

A lot of people here use bleach -- you just have to be extra, extra sure to wash it thoroughly. Rinse until there is no bleach smell left on anything, and then rinse it a few more times for good measure.

Personally I've never used it because I'm too terrified of bleach residue being left behind, so I use vinegar instead and multiple washings/rinsings. It's potentially safer as far as the risk of residue goes, but you aren't guaranteed quite as well that 100% of contaminants will be gone. You just kind of have to weigh the risks for yourself.